High density polyethylene films which are biaxially oriented in a balanced fashion to a degree of greater than 6.5 times in both the machine direction (MD) and the transverse direction (TD) are described in British Pat. No. 1,287,527.
U.S. Pat. No. 4,680,207 relates to imbalanced biaxially oriented films of linear low density polyethylene oriented up to six times in the machine direction, and up to three times in the transverse direction but less than in the machine direction.
Blown films of HDPE having a ethylene-vinyl acetate heat seal coating used for food packaging but such films must have a thickness of about two mils to meet the water vapor transmission (WVTR) requirements for packaging suitable for dry foods such as cereals. Moreover, blown HDPE films do not exhibit the dead-fold properties desirable in food packages particularly of the bag-in-box type.
In accordance with this invention, good WVTR properties can be achieved in HDPE film of about one mil thickness. The films also have dead-fold characteristics which make them well suited for packaging of foods in bag-in-box operations conducted on vertical, form, fill and seal (VFFS) machinery.